Conventionally, transfer of streams based on MPEG has been carried out as follows. An input analog stream is digital-converted into a form of a partial transport stream (hereinafter referred to as a partial TS). Then, the MPEG partial TS is transferred directly (or after being digital-recorded in a DVHS tape or the like as required) through a digital interface. The partial TS is composed of packets of elementary streams (hereinafter referred to as ES packets) of video and audio analog streams, and packets of predetermined information tables (hereinafter referred to as information packets), and each packet is identified by a parameter such as “table id” that is present in a header of the packet.
Examples of typical data formats of information tables included in partial TS are as follows: a program association table (hereinafter referred to as PAT) and a program map table (hereinafter referred to as PMT) which are standardized by STD-B10 of Association of Radio Industries and Businesses (ARIB); and a discontinuity information table (hereinafter referred to as DIT) and a selection information table (hereinafter referred to as SIT) which are standardized by STD-B21 of ARIB.
FIGS. 4 to 7 illustrate the formats of the above-mentioned information table packets, i.e., PAT, PMT, DIT, and SIT, respectively.
As shown in FIGS. 4 to 7, the information packets contain various kinds of information indicating the contents of the partial TS to be transferred. When the transfer status of the partial TS changes, the information in the information packets are altered so as to reflect the contents of the partial TS being transferred (refer to Japanese Published Patent Application No. Hei. 10-145755 (Page 9, FIG. 1), and Japanese Published Patent Application No. 2003-92738 (Page 18, FIG. 1)).
In the conventional data output control apparatus, however, it is difficult to recognize the transfer status of the partial TS, when the transfer status of the partial TS changes and thereby the information packets are altered. Therefore, it is difficult to judge when alteration of the information packets has been carried out.
Further, in the conventional data output control apparatus, when the transfer status of the partial TS changes, alteration of the corresponding information packet is carried out based on comparison with a specific packet ID. Therefore, for example, when the number of packets of the respective information tables changes, the process of altering the information packets cannot satisfactorily follow the change in the number of packets.